Large quantities of liquids containing unfiltered solid particles, such as liquid waste, in the past have been discharged in the environment without filtration separation. Current federal and state regulations limit the discharge of such liquids and liquid wastes into the environment. U.S. Pat. No. 4,465,605 is directed to filtration of solids from waste with biogenetic silica, such as rice hull ash, which provides good filtration. U.S. Pat. No. 5,362,407 is directed to gravity clarifiers or separators for gravity separating solid particles in liquids, such as oil or oil and water.
Waste waters containing large quantities of hazardous metals have been discharged in the environment without treatment. Current federal and state regulations limit the hazardous metal concentrations in waste water and are extremely severe and are frequently based on analytical detection limits. Most metals are present in the waste water concentrations which can range from 10 to 4000 parts per million. Under some current regulations, all hazardous metal concentrations in waste water are required to be less than 300 parts per million and some to less than 1 part per billion. The hazardous materials include cadmium, chromium, copper, lead, manganese, selenium, as well as others. In addition, it is desirable to remove and sequester into the removed solids (filter cake) all metals, some of which are currently considered to be nonhazardous, such as zinc. U.S. Pat. Nos. 5,106,510 and 5,207,910 are directed to combined filtration and fixation of heavy metals.
European patent application (PCT) published on Dec. 29, 1993 under Publication No. 0575329 is directed to a filter aid or medium and a method of filtering liquid wastes which have good filtration, good flow rates through the filter cake, and have a heat value of the resulting filter cake containing the filtered solids of at least 5000 Btu per pound of filter aid; and this qualifies as a fuel for industrial boilers, furnaces, and kilns. Combustible filtering particles, such as rubber particles, in a size effective to filter the particles, alone or with up to about 70 percent silicious filtering particles, are set forth.
Coagulation/flocculation agents are utilized in water filtration and clarification applications. Coagulation and flocculation are essentially an electro-physical phenomena where particles of like electrostatic charge are pulled together using an agent with the opposite charge. Thus, the charged contaminated particle and the flocculating agent draw together and combine to make a larger and heavier particle or aggregate. Since larger and heavier particles are generally the easiest to settle out of and separate from waste water, such as by gravity separation or by filtering, this separate flocculation technology is common in water treatment.
Both natural and synthetic coagulation/flocculation agents have been used. Commonly used synthetic flocculating agents are organic based high molecular weight polyacrylamides, polyamines, amine quaternary ammonium and others. These polymers are soluble in water and can be manufactured with specifically designed charge polarity and magnitude. Polymers are commonly sold in dry, emulsion, and liquid form. Polymeric water treatment flocculation chemicals are a huge commercial industry with many large and small companies involved in the manufacture and sales of the product. Among natural coagulation/flocculation agents are natural clay type polymers from Cetco (a division of American Colloid), Biomin, and Southern Clay, natural alums, iron, sulfates, ferric chloride, calcium chloride and swelling clays. These coagulation/flocculation agents can be cationic, anionic, or nonionic and are added separately to the waste water to be filtered or cleared.
Coagulation/flocculation agents when added to waste water separately or by themselves are difficult to use because of their complicated and troublesome material handling characteristics. In dry form, synthetic polymers have to be diluted twice prior to use. The first dilution is critical because the particles have to be individually wetted or they will flock themselves prior to complete dispersion making an ineffective mess. There is no recovery from this development; and when it occurs, the mess must be discarded, which is a problem in and of itself, and the process started again.
Liquid and emulsion polymers largely solve this problem, but they generate problems of their own. They dramatically raise the costs of using organic polymers. Also, the liquid and emulsion products cannot be made as concentrated dry products so more pounds of liquid/emulsion polymers are required for a reaction equivalent to the former.
In both cases polymer solutions are extremely slippery, sticky, and tenacious materials that create serious safety hazards if spilled. When overdosed, they tend to create undesirable consequences involving the contaminant particles, that are stringy, clumpy floccs in waste water equipment. If extremely overdosed, the excess polymer gets onto apparatus surfaces which creates problems especially if the excess gets into filter screens and cloths which it clogs thus interrupting the filtration operation.
Although polymer flocculation is quite effective at massing smaller particles into larger, more manageable, or filterable particles, there are additional problems. Polymer formed floccs are gelatinous, deformable globs that are quite delicate to handle. If over agitated, the floccs degrade to smaller particles that are difficult to remove. Even in their largest form they are deformable which makes them difficult to filter. Thus, flocculation makes large aggregates that are easier to filter but makes deformable aggregates that are difficult to filter.
In addition, in many waste water treatment operations, polymers are only one of the chemicals added. Precipitants, oxidizers, and other agents are often included in the treatment protocol. In a great many occasions, filter aids are also required to defeat the problems created by the deformable nature of the floccs.
It would be highly desirable to provide a combined flocculating and clarifying medium which has the advantages of flocculation and coagulation of smaller particles into larger aggregates which do not deform under the conditions of use, such as in filtering, and add weight so that they readily settle or sink in the waste water in gravity separation, and methods of separating solids from waste waters, such as by gravity or filtering which avoids problems involved with the separate application of coagulant/flocculating agents to waste waters in removing solids from them.